1. Field of Invention
The invention relates to the compression and presentation of a raster type image, for example a newspaper replica or scanned documents.
2. Description of Related Art
The compression of images is generally performed by using a single algorithm for the compaction of data across the entire image area. A result of this is that an image containing tone, images and text is compressed for example with a JPEG algorithm, which is known for its text smudging effect. On the other hand, algorithms that work well in text compression are poorly applicable to the compression of a photograph.
Segmentation is often used for the reason that, in the process of producing an image, different areas are compressed with different methods, whereby text, for example, is displayed by means of bitmap or vector fonts and a single file can be adapted to contain vector graphics images and images compressed from a bitmap. For example, a document produced by an office or makeup program contains sections compressed in a variety of ways.
Segmentation is also used in the compression of images, such that, within a single image file, a section-by-section movement with respect to the preceding image is identified and the unchanged section is omitted from reproduction. Likewise, parts most important to the human eye, for example a face, can be identified in a section-by-section manner from an image and compressed at a higher accuracy than the rest of the image. This segmentation can be executed within a single MPEG or JPEG file.